HELP!! Bad Knee, I have no idea how to workout now

Short Story: I have to wait to get in to see a doctor to find out how bad my knee is and how long it will take to hopefully get back to 90% (it hasnt been 100% since my mid 20s)

I really need help on how to workout without the big lifts. I'm totally lost at what to do and how to workout in the gym. My stubbornness has made me try to power through squats and deads but I'm doing more harm than good and the weight I'm lifting is pathetic.

If anyone can help give me some advice as to how to set up a workout program that would be great.

Again it can't involve anything with the lower body, I cant even do leg extensions without being in pain.

Can you do any exercises while standing provided it doesn't involve knee flexion or extension? If can do this I would recommend some rack pulls or RDL's as these will involve mostly hamstrings, glutes, and back but still have a somewhat full body effect. I would also recommend bent-over rows with your back parallel to the floor and the bar returned to the floor after every rep. You could also do standing military presses. If you can do these things at least your posterior chain and midsection strength will stay decent.
If you can't do these things then you are pretty much stuck with upper body isolation exercises.